Wednesday, December 28, 2016

New Gear: DigitalMate 500mm/1000mm f/8 Manual Telephoto Lens

I got this DigitalMate 500mm (1000mm with 2x converter) f/8 manual telephoto lens for Christmas and I'm keen to try out the impressive 1000mm reach on some night sky objects. With an aperture range of f/8 to f/32, this is going to be extremely useful for lunar, planetary, and solar observing. It could be useful for double and triple stars as well, but maybe not so great for faint deep sky objects. I can't wait to try it out at night to see how it compares to my Meade 285 refractor, not just in focal length but also the quality of the glass to hopefully cut down on chromatic aberration.

Be careful with your terminology, it would be a photography faux pas to call this a 'zoom' lens because the focal length is fixed. It's either 500mm or 1000mm with the converter, but nothing in between.

Here is a closer look and some 'unboxing' type photos showing off my new toy, including some close ups of the important features, and down below are my first test shots.

The lens is so long that it comes with a bracket to mount the lens itself on a tripod to counter balance the weight of the camera body. Although the lens is quite long and heavier than other lenses, with the 2x converter, the length is off balance and I haven't found a way to slide the ring up any further - I only manage to twist it about.

Close up of the thumb screw and collar attachment for the main shaft of the lens

On the top of the lens, you see what looks like focal length zoom adjustments, but remember this is a fixed focal length, so these settings are the manual focus notches showing the distance your subject should be at to be in focus.

Manual focus and manual f/number controls

My kit came with a t-ring, this connects the regular Canon EF lens threads to the shaft of the lens with a narrower thread. It's a simple go-between so the lens makers can make different size t-rings to fit the same lens on different cameras without re-designing the lens itself. A t-ring is also how I attach my DSLR to my telescope.

Let's take a look at that 2x converter. It looks like an eyepiece at first, but it's threaded to screw on between the lens and the t-ring. I think these things are sometimes called extenders because they literally extend the length of the lens tube and then angle it through another lens before it gets to the camera sensor (just like an eye piece).

2x converter contains a small lens sorta like an eyepiece

Camera body and 2x converter

Ok, so let's test it out. First of all, when I finally got the thing on a tripod it was difficult to aim and focus. I felt like I was wielding a water canon or some kind of turret gun, and reaching to near the end of the lens to manually focus was a little clunky. For the sake of the test shots, I made it work and did my best to focus - but in the future, I think this is the kind of thing that needs to go on a mount and not just a tripod.

Target (below) circled in red in this iPhone photo for comparison

500mm vs. 1000mm telephoto lens

However, the 2x converter certainly does the trick, and the extra reach of the 1000mm focal length is impressive. Adding the converter completely changes the exposure, so I haven't figured out the 1:1 settings just yet. Do you recognize the top of the grain elevator from my moon set or sunset photos? It's one of my favorite backyard targets because it's actually a ways off across the street from the housing division but just visible between the roofline.

Here's the DigitalMate 500mm with 2x converter on my EQ-1 mount - it's a little more stable. I was making a go at Venus in the early night sky. It certainly feels more like a telescope than a lens!

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